The present invention relates to a method of reducing an epoxy group-containing organic compound with hydrogen. More particularly, the present invention relates to a method of reducing an epoxy group-containing compound, particularly an epoxy group-containing cycloaliphatic compound, with hydrogen in the presence of a nickel catalyst, with high efficiency, to thereby produce a target compound, particularly a cycloaliphatic saturated alcohol, at high selectivity. The compound, particularly the cycloaliphatic saturated alcohol, produced by the method of the present invention can be converted to, for example, a lactam compound, a lactone compound or a dibasic organic acid, which are useful as materials for producing polyester or polyamide synthetic fibers or resins.
A cycloaliphatic alcohol, for example, cycloalkanol can be produced by a method in which a cycloalkane corresponding to the alcohol is oxidized with air in the presence of a boric acid catalyst. The conventional air oxidation method is, however, disadvantageous in that since a plurality of types of by-products are produced in a large amount due to successive reactions, and thus the conversion of the cycloalkane must be controlled to a low level, the target cycloalkanol is obtained only in a low yield and the reaction result is unsatisfactory. For example, when cyclododecane is oxidized with air in the presence of a boric acid catalyst, the target cyclododecanol and cyclododecanone are obtained only in a total yield of about 20%. On the other hand, since an epoxycycloalkane and/or an epoxycycloalkene can be produced with a high yield by an epoxidizing reaction of a cycloalkene, if the epoxy compound can be converted to a cycloalkanol with a high efficiency, the cycloalkanol can be produced from the cycloalkene with a high yield.
However, there are few reports concerning the method of converting the epoxycycloalkane and/or epoxycycloalkene to the cycloalkanol.
For example, Japanese Examined Patent Publication No. 47-38, 437 discloses a hydrogenation method in which hydrogen is brought into contact with epoxycyclododecane, to produce cyclododecanol and isomerized cyclododecanone, and in which method, Raney nickel is used as a catalyst.
The Japanese publication, however, does not indicate the yields of the cyclododecanol and cyclododecanone. Therefore, the method of the Japanese publication was carried out by the inventors of the present invention. As a result, it was found that, in the hydrogen-reduction procedure of the epoxycyclododecane compound, a disoxidation reaction of the epoxy group occurred and various hydrocarbons, for example, cyclododecane were produced as by-products in a large amount, and thus the selectivity to the target compounds, namely cyclododecanol and cyclododecanone was unsatisfactory.
Also, Neftekhimiya, 16(1), 114-119, 1976, discloses a method of reducing 1,2-epoxy-5,9-cyclododecadiene with hydrogen by using a nickel catalyst carried on chromium oxide. This method uses a toxic chromium compound and thus is difficult to utilize in practice.
Generally, it is well known that in a hydrogenation reaction of the epoxy compound in the presence of a nickel catalyst, various types of by-product compounds are produced in a large amounts due to disoxidation reaction of the epoxy compound (Tokyo Kagaku-dojin, LECTURE ON ORGANIC REACTION MECHANISM 13, CATALYTIC REACTIONS ((Second Volume), written by Mikio Mitsui).
Further, in J. Mol. Catal., Vol. 69, pages 95-103 (1991), a report concerning hydrogenation of epoxycyclododecadiene is described.
In a reaction example shown in this report, when epoxycyclododecadiene is subjected to a reduction reaction with a hydrogen gas in the presence of a palladium catalyst carried on xcex3-alumina under a reduced pressure of 1.3 MPa at a reaction temperature of 90xc2x0 C., cyclododecanol is obtained at a yield of 20%. In the report, a palladium catalyst carried on titania and a palladium catalyst carried on silica were employed. In each case, the yield of the cyclododecanol was less than 20%.
Further, in a Drafted Report, page 68, of the 24th xe2x80x9cProgress in Reaction and Synthesisxe2x80x9d Sympodium, Nov. 5 to 6, 1998, a hydrogenation reaction of an epoxycyclododecadiene in the presence of a palladium catalyst carried on a carbon material is reported. In this case, the target cyclododecanol was produced at a yield of 5%.
As mentioned above, it is known that the yield of the cyclododecanol by the catalytic hydrogenation reaction of the epoxycyclododecadiene with a hydrogen gas is extremely low.
Furthermore, as an analogous reaction, a method of synthesizing cyclohexanol by a hydrogenation reaction of an epoxycyclohexane is reported in Synthetic Communication, 25(15), p 2267-2273, (1995).
In the method of the publication, it is reported that when an epoxycyclohexane was reduced with ammonium formate (HCOONH4) in the presence of a palladium catalyst carried on activated carbon, the yield of the resultant cyclohexanol was 50%. In this method, however, ammonium formate (HCOONH4) used as a hydrogen-supply source is expensive, the yield of the cyclohexanol obtained by using the expensive hydrogen-supply source is low, and therefore, this method cannot be utilized as a practical method of producing cycloalkanol to be used as a material for producing a lactam.
As mentioned above, a method of producing a hydrogen-reduced compound at a high yield by catalytically reacting an epoxy group-containing organic compound with a hydrogen gas, which is cheap, as a hydrogen-supply source has not yet established, and thus the development of this method is in strongly demand.
An object of the present invention is to provide a method of catalytically reacting an epoxy group-containing organic compound with hydrogen to produce a corresponding hydrogen-reduced compound with a high yield.
A further object of the present invention is to provide a method of catalytically reacting an epoxy group-containing organic compound with hydrogen, while a production of a by-product comprising hydrocarbon compounds due to a disoxidation reaction of the epoxy group-containing organic compound is restricted, to produce a target hydrogen-reduced product at a high yield.
The above-mentioned objects can be attained, by the hydrogen-reduction method of the present invention, for an epoxy group-containing organic compound.
The method of the present invention for reducing an epoxy group-containing organic compound with hydrogen comprises bringing an epoxy group-containing organic compound into contact with hydrogen in the presence of a nickel catalyst, to reduce the epoxy group-containing organic compound in a hydrogen reduction reaction system, in which the reduction reaction system further comprises a basic substance.
In the method of the present invention, the basic substance preferably comprises at least one member selected from the group consisting of hydroxides of alkali metals, carbonates of alkali metals, alkoxides of alkali metals, hydroxides of alkaline earth metals, carbonates of alkaline earth metals, amine compounds having 1 to 3 alkyl groups each having 1 to 12 carbon atoms, and basic oxides of alkaline earth metals and rare earth elements.
In the method of the present invention, the basic substance is preferably present in a total molar amount of 0.01 to 10 times the molar amount of nickel atoms contained in the nickel catalyst.
In the method of the present invention, in the hydrogen reduction reaction system, the basic substance may be carried on the nickel catalyst.
In the method of the present invention, the epoxy group-containing organic compound is preferably selected from epoxy group-containing saturated and unsaturated cycloaliphatic organic compounds having 5 to 20 carbon atoms.
In the method of the present invention, the epoxy group-containing organic compound is selected from the group consisting of, for example, epoxycyclododecane, epoxycyclododecene, epoxycyclododecadiene, epoxycyclohexane, epoxycyclohexene, epoxycyclooctane, and epoxycyclooctene.
In the method of the present invention in which an epoxy group-containing organic compound is brought into contact with hydrogen in the presence of a nickel catalyst to reduce the compound with hydrogen in a hydrogen reduction reaction system, it is important that the reduction reaction system further comprises a basic material.
The epoxy group-containing organic compound used as a starting compound for the method of the present invention is preferably selected from epoxy group-containing saturated and unsaturated cycloaliphatic organic compounds having 5 to 20 carbon atoms, more preferably 5 to 12 carbon atoms, still more preferably 6 to 12 carbon atoms. The epoxy group-containing cycloaliphatic organic compounds include, for example, epoxycyclododecane, epoxycyclododecene, epoxycyclododecadiene, epoxycyclohexane, epoxycyclohexene, epoxycyclooctane, and epoxycyclooctene. These compounds may have at least one substituent, preferably 1 to 3 substituents, each consisting of an alkyl group, preferably an alkyl group having 1 to 4 carbon atoms. The above-mentioned compound may be employed alone or in a mixture of two or more thereof. Also, these compounds include a plurality of isomers. There is no limitation to the type of the isomers.
The nickel catalyst may be selected from Raney nickel, nickel oxide and stabilized nickel which are effective, as nickel catalysts, for hydrogenation reactions. Particularly the stabilized nickel is preferably employed. The stabilized nickel is advantageous for the method of the present invention in that it is stable and safe in air. The above-mentioned types of nickel catalysts may be employed alone or in a mixture of two or more thereof.
Also, the nickel catalyst may be carried on a carrier comprising at least one member selected from the group consisting of activated carbon, diatomaceous earth and metal oxides.
The above-mentioned materials for the carrier may be employed alone or in a mixture of two or more thereof.
In the method of the present invention, the metal oxides usable as a carrier for the nickel catalyst include alumina, silica, zirconia, titania, zeolite, titanosilicate, magnesia and mixtures thereof. Preferably, alumina, silica, zeolite and mixtures thereof are employed, more preferably, alumina is employed. With respect to the type of alumina usable for the present invention, xcex3-alumina and xcex1-alumina are usable and, preferably, xcex3-alumina is employed.
The nickel-carried catalyst usable for the method of the present invention can be prepared by conventional methods. For example, a nickel oxide-carried catalyst is prepared by impregnating a carrier with an aqueous solution of nickel nitrate in a desired amount; evaporating, drying and solidifying the nickel nitrate-impregnated carrier; and calcining the dried nickel nitrite-impregnated carrier. Also, a metal nickel-carried catalyst can be prepared by reducing a nickel oxide-carried catalyst with hydrogen by a conventional method. The amount of nickel contained in the nickel catalyst is preferably 0.1 to 90% by weight, more preferably 5 to 70% by weight, still more preferably 10 to 70% by weight, in terms of metallic nickel, based on the weight of the carrier. When the amount of nickel in the catalyst is less than 0.1% by weight, the resultant catalyst may exhibit an insufficient catalytic activity.
In the nickel catalyst usable for the method of the present invention, the metal oxide usable as a carrier for the catalyst preferably has a specific surface area of 10 m2/g or more, more preferably 50 to 450 m2/g. The specific surface area can be determined by a nitrogen BET method.
When the nickel catalyst used for the method of the present invention is carried on an alumina carrier, the alumina carrier preferably has a specific surface area of 10 m2/g or more, more preferably 50 m2/g or more, still more preferably 80 to 450 m2/g. The above-mentioned alumina may be aluminum oxide prepared by heat-treating aluminum hydroxide. This type of aluminum oxide may be one produced during a procedure for preparing a nickel-carried catalyst by using aluminum hydroxide. The alumina carrier may contain a small amount of Na, Mg, Fe and SiO2. When the content of these impurities is several % or less, they do not impart a great influence on the catalytic performance of the catalyst. When alkali metals and/or alkaline earth metals are contained, they may impart a good effect on the catalytic performance of the catalyst. Also, a composite oxide containing alumina and a metal oxide other than alumina may be used as a carrier for the catalyst for the method of the present invention, as long as the composite oxide has a specific surface area of 10 m2/g or more.
The amount of nickel carried on the alumina carrier is 0.1 to 90% by weight, preferably 5 to 70% by weight, more preferably 10 to 70% by weight, based on the weight of the alumina carrier. The nickel-carried catalyst may be used without pretreatment, or after a pretreatment, for example, an alkali addition treatment or a hydrogen-reduction treatment.
The nickel catalyst usable for the method of the present invention may be in the form of a powder, or of shaped pellets. Generally, the powder nickel catalyst is used in a liquid phase suspension bed catalytic reaction, and the pellet-shaped catalyst is used in a fixed bed catalytic reaction. In the fixed bed catalytic reaction, a trickle reaction, a liquid phase reaction and a gas phase reaction can each be carried out under certain conditions.
In the case of the powder catalyst usable for the liquid phase suspension bed reaction, the catalyst particles preferably have an average particle size of 5 xcexcm to 300 xcexcm. In the case of the pellet-shaped catalyst usable for the fixed bed catalytic reaction, the pellets preferably have an average length of 1 to 10 mm.
In the method of the present invention, there is no limitation to the amount of the nickel catalyst used for the method. Generally, when a liquid phase suspension bed-type reactor is used, the ratio of the molar amount of nickel atoms contained in the nickel catalyst to the molar amount of the epoxy group-containing organic compound used in the reactor is preferably 1/300,000 or more, more preferably 1/10,000 or more, still more preferably 1/5,000 to 2/1. When the amount of the nickel catalyst is too small, the resultant catalytic effect may be insufficient, when it is too large, the catalytic effect may be saturated, and an economic disadvantage may occur. Also, in the case where the liquid phase suspension bed is employed, a disadvantage, that a load on a stirrer becomes too high, may occur.
In the method of the present invention, a basic substance is contained in the reduction system. The basic substance contained in the reduction reaction system contributes to restricting a disoxidation reaction and to enhancing the yield of the target compound produced by the hydrogen reduction reaction.
The basic substance usable for the method of the present invention preferably comprises at least one member selected from hydroxides of alkali metals, carbonates of alkali metals, alkoxides of alkali metals, hydroxides of alkaline earth metals, carbonates of alkaline earth metals, amine compounds having 1 to 3 alkyl groups each having 1 to 12 carbon atoms, and basic oxides of alkaline earth metals and rare earth elements.
The basic compounds as mentioned above include, for example, hydroxides of alkali metals and alkaline earth metals, for example, sodium hydroxide, lithium hydroxide, potassium hydroxide, barium hydroxide and strontium hydroxide; carbonates of alkali metals and alkaline earth metals, for example, sodium carbonate, potassium carbonate and barium carbonate; alkoxides of alkali metals, for example, sodium methoxide and sodium ethoxide; aliphatic amine compounds, for example, triethylamine, and tributylamine; and basic oxides, for example, magnesium oxide, barium oxide, cerium oxide. Preferably, alkali metal hydroxides and alkali metal alkoxides are employed and more preferably alkali metal hydroxides are employed. These basic compounds may be employed alone or in a mixture of two or more thereof.
In the method of the present invention, the amount of the basic substance is established in response to the molar amount of nickel atoms contained in the nickel catalyst. Preferably the total molar amount of the basic substance is 0.01 to 10 times, more preferably 0.05 to 5 times, still more preferably 0.05 to 1.0 times, further preferably 0.05 to 0.5 times, the molar amount of nickel atoms contained in the nickel catalyst. If the amount of the basic substance is less than 0.01 times in mole, the resultant restricting effect on the disoxidation reaction for the reduction reaction system may be insufficient and the resultant yield of the target compound may be unsatisfactory. Also, if the basic substance is used in an amount more than 10 times in mole, not only the effect of the basic substance may be saturated, and an economical disadvantage occurs but, also, disadvantages such as the catalytic activity significantly decreases, and the amount of by-products generated from the epoxy group-containing organic compound increases, may occur.
In the method of the present invention, the basic substance may be carried on the nickel catalyst. To carry the basic substance on the nickel catalyst, the nickel catalyst may be immersed in an liquid (for example, an aqueous solution or an organic solvent solution) containing the basic substance and dried to produce the nickel catalyst impregnated with the basic substance-containing liquid. In this method, there is no limitation to the immersion temperature. Generally, the immersion is preferably carried out at a temperature of 0 to 100xc2x0 C., more preferably 0 to 30xc2x0 C. Also, there is no limitation to the drying conditions. The drying may be carried out in the ambient air atmosphere or an inert gas atmosphere, as long as the drying can be effected uniformly. Preferably, the drying temperature is 60 to 120xc2x0 C. The solvent for dissolving the basic substance may be selected from a liquid inert to the basic substance, for example, water, ethyl alcohol or a mixture of water with ethyl alcohol.
When, as a basic substance, a basic oxide of an alkaline earth metal is employed, the nickel catalyst is immersed in an aqueous solution of an alkaline earth metal salt in a desired concentration; to this aqueous solution, an aqueous solution containing hydroxyl ions is added to cause a resultant hydroxide of the alkaline earth metal to be precipitated on the nickel catalyst surface; the resultant precipitate is filtered and washed; and the resultant solid is uniformly dried in the ambient air atmosphere or an inert gas atmosphere, or under reduced pressure, to produce a basic substance-carrying nickel catalyst.
Also, when, as a basic substance, a basic oxide of an alkaline earth metal is employed, a nickel catalyst carrying thereon a hydroxide of the alkaline earth metal is uniformly heated in the ambient air atmosphere or an inert gas atmosphere to heat-decompose the alkaline earth metal hydroxide, and to provide a nickel catalyst carrying thereon the basic oxide of the alkaline earth metal.
In the method of the present invention, the basic substance-carrying nickel catalyst is preferably reduced with hydrogen before the catalyst is employed for the hydrogen reduction reaction in accordance with the method of the present invention. The hydrogen reduction pretreatment for the nickel catalyst is preferably carried out at a temperature of 50 to 1000xc2x0 C., more preferably 70 to 800xc2x0 C., still more preferably 100 to 700xc2x0 C. The hydrogen reduction pretreatment may be effected in such a manner that the nickel catalyst is placed in a fixed bed flow type reactor, and a hydrogen gas passes through the reactor, or that the nickel catalyst is placed in an autoclave and dispersed in an inert solvent (for example, normal hexane and cyclohexane) and a hydrogen gas is charged in the autoclave or passed through the dispersion in the autoclave while the dispersion is stirred.
When the catalyst to be subjected to the hydrogen reduction pretreatment is dried, the drying may be effected simultaneously with the reduction in the hydrogen gas atmosphere in accordance with the above mentioned method. However, preferably, the catalyst is preliminarily dried and then subjected to the hydrogen reduction.
The reduction-treated nickel catalyst may be directly used for the reduction reaction. Alternatively, the reduction-treated nickel catalyst may be subjected to a stabilization treatment with an oxygen-containing gas in accordance with a conventional method and then used for the reduction reaction. Also, the catalyst may be shaped in the form of a sphere or a pellet, in response to the type of reactor and the reaction conditions for the reduction reaction of the method of the present invention.
In the method of the present invention, the hydrogen reduction reaction of the epoxy group-containing organic compound may be carried out in an organic solvent or without using the organic solvent. The organic solvent is preferably selected from those which do not affect the the hydrogen reaction in accordance with the method of the present invention, and does not cause production of by-products. The above-mentioned type of organic solvents include, for example, liquid alkanes, for example, n-hexane, n-heptane and cyclohexane; ethers, for example, dimethylether and dixoane; alcohols, for example, propyl alcohol and butyl alcohol; and esters, for example, ethyl acetate and butyl acetate. These organic solvents may be employed alone or in a mixture of two or more thereof. When the reaction solvent is employed, the reaction may be easily controlled. The organic solvent is preferably used in an amount of 100 times or less, more preferably 10 times or less, the weight of the epoxy group-containing organic compound.
The method of the present invention can be carried out by using a batch type reactor or a continuous reaction apparatus, for example, a liquid phase suspension bed type reactor, a fixed bed flowing type reactor or a trickle bed-type rector. In these types of reactors, as mentioned above, the reaction solvent may be employed or not employed.
In the method of the present invention, the starting material containing the epoxy group-containing organic compound may further contain the corresponding reaction products, such as alkanone compound and/or alkanol compound.
In the method of the present invention, the epoxy group-containing organic compound is mixed with a nickel catalyst and a basic substance or a basic substance-carrying nickel catalyst, the mixture is heated under the ambient pressure or a pressure higher than the ambient pressure, optionally while the mixture is stirred, to subject the mixture to a reaction. In this method, the reaction temperature is preferably 80 to 280xc2x0 C., more preferably 100 to 250xc2x0 C., still more preferably 100 to 230xc2x0 C., further preferably 110 to 200xc2x0 C. Also, in the method of the present invention, the pressure of hydrogen is preferably 98 to 98,000 kPa (1 to 1,000 kg/cm2) more preferably 490 to 39,000 kPa (5 to 400 kg/cm2), still more preferably 980 to 20,000 kPa (10 to 200 kg/cm2).
When the reaction pressure and/or temperature are too low, the hydrogenation reaction for the epoxy groups and the double bonds of the epoxy group-containing organic compound may be insufficiently effected and the target compound may be obtained in an insufficient yield. Also, when the pressure is too high, the hydrogen reduction reaction is sufficiently effected, but the effect of the pressure may be saturated and an economical disadvantage may occur. When the temperature is too high, the amount of by-products, for example, compounds having a high boiling temperature may increase. There is no specific limitation to the reaction time and contact time. Usually, a sufficient reaction time is 3 hours or less.
In the method of the present invention, the reaction products are optionally isolated from the reaction system by, for example, distillation and/or crystallization and are refined.